Investigation of insulin resistance in patients with normocalcemic primary hyperparathyroidism.

While derangements in glucose metabolism in patients with primary hyperparathyroidism are well-defined, this issue is not investigated in patients with normocalcemic primary hyperparathyroidism (NPHPT). The aim of this study was to investigate the presence of insulin resistance in patients with NPHPT. Eighteen patients with NPHPT (two males and 16 females) and 18 healthy volunteers were enrolled into the study. Secondary causes of parathyroid hormone elevations were excluded in all patients. Blood samples were obtained for the measurement of serum calcium, phosphate, alkaline phosphatase (ALP), albumin, creatinine, glucose, and serum lipid levels. Glucose and insulin responses to oral glucose tolerance test (OGTT) were obtained. Homeostasis model assessment (HOMA-IR) was also used as an indice of insulin resistance. Patients and control subjects had similar age, body mass index, and sex distribution. Although within normal limits, serum calcium and ALP levels were higher in patients than in the control subjects. None of the patients and the control subjects had diabetes mellitus, while eight patients and six control subjects had impaired glucose tolerance. Insulin responses to OGTT and HOMA-IR were not significantly different among the patient and control subjects. In addition, both groups have similar serum lipid levels. Patients with NPHPT do not exhibit insulin resistance and glucose intolerance. Since so little is known about this form of disease, subjects should be monitored regularly for the metabolic aspects of the disease as well as the progression of their disease.